Micro-electro-mechanical-system device with guard ring and method for making same

1. A MEMS device with guard ring, comprising: a substrate including transistor devices, part of interconnection and MEMS structure; a top dielectric layer formed on the substrate, part of the top dielectric layer being etched to release the MEMS device; a top metal layer, part of the top metal layer forming a bond pad; a sidewall on, surrounding and connecting with the bond pad, the sidewall being disposed on and along all sides of the bond pad to extend upward from the bond pad in a direction opposing to a downward direction from the bond pad toward the substrate, to form a guard ring extending upward from the bond pad, wherein the sidewall is made of metal or amorphous silicon resistive to an etchant capable of etching the top dielectric layer and is formed before the etching of the top dielectric layer; and a shielding layer provided on the top dielectric layer and connected with the sidewall, wherein the shielding layer is a composite layer including an upper layer made of metal or amorphous silicon and a lower layer made of an insulating material resistive to an etchant capable of etching the top dielectric layer, wherein the upper layer does not electrically connect the top metal layer.

2. The MEMS device of claim 1 , wherein the guard ring is made of a material of metal, amorphous silicon, silicon nitride, silicon oxynitride, or a composite material of two or more of the above materials.

3. The MEMS device of claim 1 , wherein the top dielectric layer includes a left-out area outside of the sidewall.

4. The MEMS device of claim 1 , wherein the top dielectric layer is made of an oxide.